1. Field of the Invention
The present invention relates generally to automatic steering, and in particular to a system and method for providing GPS-based guidance for an auxiliary steering system, which is installed in parallel with a primary steering system of a vehicle and utilizes a constant factor, such as the vehicle steering rate, in a control system with a feedback loop.
2. Description of the Related Art
In the field of vehicle guidance and navigation, the Global Positioning System (GPS) has enabled a wide range of applications. For example, various GPS receivers are available for aviation, marine and terrestrial vehicles. The GPS information provided by such receivers can be processed and used for navigation. In more sophisticated systems, vehicle guidance can be automatically controlled using such information. For example, a predetermined travel or flight path can be programmed into an on-board computer. The vehicle guidance system can automatically maintain appropriate course parameters, such as course, heading, speed, altitude, etc. Control system, feedback theory and signal filtering techniques can be used to interactively anticipate (with higher order systems) and compensate for course deviations and navigation errors. Such sophisticated autopilot and automatic steering systems tend to involve powerful computers and complex flight and steering controls integrated with manual controls.
Accurate vehicle and equipment guidance is an important objective in agriculture. For example, tilling, planting, spraying, fertilizing, harvesting and other farming operations typically involve specialized equipment and materials, which are operated and applied by making multiple passes over cultivated fields. Ideally, the equipment is guided through accurately-spaced passes or swaths, the spacing of which is determined by the swath width of the equipment. Gaps and overlaps can occur when operators deviate from the ideal guide paths, resulting in under-coverage and over-coverage respectively. Such gaps and overlaps are detrimental to agricultural operations and can reduce crop yields. For example, gaps in coverage reduce the effective areas of fields being cultivated and treated. Overall crop production may suffer as a result. Overlaps in coverage tend to be inefficient and wasteful of materials, such as fertilizer, pesticides, herbicides, seed, etc. Another potential problem with overlapping coverage relates to the potentially crop-damaging effects of double applications of certain agricultural chemicals.
Previous systems for assisting with the guidance of agricultural equipment include foam markers, which deposit foam along the swath edges. The foam lines produced by foam markers provide operators with visible reference lines on which subsequent passes can be aligned. However, foam marking systems consume foam-making materials and provide only temporary foam marks.
GPS technology advanced the field of agricultural guidance by enabling reliable, accurate systems, which are relatively easy to use. For example, the OUTBACK S™ steering guidance system, which is available from RHS, Inc. of Hiawatha, Kans. and is covered by U.S. Pat. No. 6,539,303 and No. 6,711,501, which are incorporated herein by reference, includes an on-board computer capable of storing various straight-line and curved (“contour”) patterns. An advantage of this system is its ability to retain field-specific cultivating, planting, spraying, fertilizing, harvesting and other patterns in memory. This feature enables operators to accurately retrace such patterns. Another advantage relates to the ability to interrupt operations for subsequent resumption by referring to system-generated logs of previously treated areas.
The OUTBACK S™ GPS guidance system provides the equipment operators with real-time visual indications of heading error with a steering guide display and crosstrack error with a current position display. They respectively provide steering correction information and an indication of the equipment position relative to a predetermined course. Operators can accurately drive patterns in various weather and light conditions, including nighttime, by concentrating primarily on such visual displays. Significant improvements in steering accuracy and complete field coverage are possible with this system. However, it lacks the “hands off” capability and inherent advantages of automatic steering, which are addressed by the present invention.
Heretofore there has not been available an automatic steering system and method with the advantages and features of the present invention. In particular, there has not been available a system adapted for original equipment or retrofit installations in parallel with various vehicle hydrostatic steering configurations, which system provides automatic steering assistance using a constant factor, such as the vehicle steering rate, in a control system with a feedback loop.